patch 9.0.1515: reverse() does not work for a Stringv9.0.1515

Problem:    reverse() does not work for a String.
Solution:   Implement reverse() for a String. (Yegappan Lakshmanan,
            closes #12179)

6 files changed, 64 insertions, 1 deletions

diff --git a/src/list.c b/src/list.c
index ca4352672..7042965ba 100644
--- a/src/list.c
+++ b/src/list.c
@@ -2999,6 +2999,8 @@ f_reverse(typval_T *argvars, typval_T *rettv)
 
     if (argvars[0].v_type == VAR_BLOB)
 	blob_reverse(argvars[0].vval.v_blob, rettv);
+    else if (argvars[0].v_type == VAR_STRING)
+	string_reverse(argvars[0].vval.v_string, rettv);
     else if (argvars[0].v_type != VAR_LIST)
 	semsg(_(e_argument_of_str_must_be_list_or_blob), "reverse()");
     else
diff --git a/src/proto/strings.pro b/src/proto/strings.pro
index a72e1ff5e..8924a2571 100644
--- a/src/proto/strings.pro
+++ b/src/proto/strings.pro
@@ -23,6 +23,7 @@ int has_non_ascii(char_u *s);
 char_u *concat_str(char_u *str1, char_u *str2);
 char_u *string_quote(char_u *str, int function);
 long string_count(char_u *haystack, char_u *needle, int ic);
+void string_reverse(char_u *str, typval_T *rettv);
 void string_filter_map(char_u *str, filtermap_T filtermap, typval_T *expr, typval_T *rettv);
 void string_reduce(typval_T *argvars, typval_T *expr, typval_T *rettv);
 void f_byteidx(typval_T *argvars, typval_T *rettv);
diff --git a/src/strings.c b/src/strings.c
index 7d4281dcd..90429d3ba 100644
--- a/src/strings.c
+++ b/src/strings.c
@@ -855,6 +855,47 @@ string_count(char_u *haystack, char_u *needle, int ic)
 }
 
 /*
+ * Reverse the string in 'str' and set the result in 'rettv'.
+ */
+    void
+string_reverse(char_u *str, typval_T *rettv)
+{
+    rettv->v_type = VAR_STRING;
+    rettv->vval.v_string = NULL;
+    if (str == NULL)
+	return;
+
+    char_u	*rstr = vim_strsave(str);
+    rettv->vval.v_string = rstr;
+    if (rstr == NULL || *str == NUL)
+	return;
+
+    size_t	len = STRLEN(rstr);
+    if (has_mbyte)
+    {
+	char_u *src = str;
+	char_u *dest = rstr + len;
+
+	while (src < str + len)
+	{
+	    int clen = mb_ptr2len(src);
+	    dest -= clen;
+	    mch_memmove(dest, src, (size_t)clen);
+	    src += clen;
+	}
+    }
+    else
+    {
+	for (size_t i = 0; i < len / 2; i++)
+	{
+	    char tmp = rstr[len - i - 1];
+	    rstr[len - i - 1] = rstr[i];
+	    rstr[i] = tmp;
+	}
+    }
+}
+
+/*
  * Make a typval_T of the first character of "input" and store it in "output".
  * Return OK or FAIL.
  */
diff --git a/src/testdir/test_functions.vim b/src/testdir/test_functions.vim
index e32c4f5ff..11cfcc953 100644
--- a/src/testdir/test_functions.vim
+++ b/src/testdir/test_functions.vim
@@ -3469,4 +3469,21 @@ func Test_delfunc_while_listing()
   call StopVimInTerminal(buf)
 endfunc
 
+" Test for the reverse() function with a string
+func Test_string_reverse()
+  call assert_equal('', reverse(test_null_string()))
+  for [s1, s2] in [['', ''], ['a', 'a'], ['ab', 'ba'], ['abc', 'cba'],
+        \ ['abcd', 'dcba'], ['«-«-»-»', '»-»-«-«'],
+        \ ['🇦', '🇦'], ['🇦🇧', '🇧🇦'], ['🇦🇧🇨', '🇨🇧🇦'],
+        \ ['🇦«🇧-🇨»🇩', '🇩»🇨-🇧«🇦']]
+    call assert_equal(s2, reverse(s1))
+  endfor
+
+  " test in latin1 encoding
+  let save_enc = &encoding
+  set encoding=latin1
+  call assert_equal('dcba', reverse('abcd'))
+  let &encoding = save_enc
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/testdir/test_listdict.vim b/src/testdir/test_listdict.vim
index b550a431f..e29c351f4 100644
--- a/src/testdir/test_listdict.vim
+++ b/src/testdir/test_listdict.vim
@@ -981,7 +981,7 @@ func Test_reverse_sort_uniq()
   END
   call v9.CheckLegacyAndVim9Success(lines)
 
-  call assert_fails('call reverse("")', 'E899:')
+  call assert_fails('call reverse({})', 'E899:')
   call assert_fails('call uniq([1, 2], {x, y -> []})', 'E745:')
   call assert_fails("call sort([1, 2], function('min'), 1)", "E1206:")
   call assert_fails("call sort([1, 2], function('invalid_func'))", "E700:")
diff --git a/src/version.c b/src/version.c
index 2d2646198..8ec68dec7 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@ static char *(features[]) =
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1515,
+/**/
     1514,
 /**/
     1513,